Interconnect structure with porous low k dielectric and barrier layer

ABSTRACT

A semiconductor device includes a semiconductor substrate, a porous low-k dielectric layer, a copper interconnect structure in the porous low-k dielectric layer, a diffusion barrier layer disposed between the copper interconnect structure and the porous low-k dielectric layer, and a silicon nitride layer disposed between the diffusion barrier layer and the porous low-k dielectric layer The low-k dielectric layer has a smooth and dense surface that increases the adhesion strength between the low-k dielectric layer and the diffusion barrier layer to improve reliability and yield of the semiconductor device.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 14/815,813, filed Jul. 31, 2015, which claims priority to Chinesepatent application No. 201410398110.8, filed Aug. 13, 2014, the contentsof which are incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor structure and method ofmanufacture, and more particularly to a semiconductor device andmanufacturing method thereof.

With the continuous decrease of semiconductor feature sizes, capacitivecrosstalk between metal interconnect layers has a significant impact onsemiconductor device performance. The use of a porous low-k dielectriclayer disposed between metal interconnect layers is a good way to solvethe problem of capacitive crosstalk.

The number of metal interconnect layers in a logic circuit of asemiconductor device may range from a few to more than 10 layers, eachof the metal interconnect layers forms a respective layer of a metalinterconnect structure. Referring to FIG. 1A, a front-end device mayhave an etch stop layer 101 disposed on a semiconductor substrate 100and a porous low-k dielectric layer 102 disposed on etch stop layer 101,a metal interconnect structure 103 is formed by dry etching in porousdielectric layer 102. Metal interconnect structure 103 includes athrough-hole 103 a and a trench 103 b. Referring to FIG. 1B, a diffusionbarrier layer 104 is formed by a physical vapor deposition process onsidewalls and bottoms of metal interconnect structure 103. Diffusionbarrier layer 104 comprises Ta/TaN. Then, a copper seed layer and acopper interconnect layer are sequentially formed. However, in theconventional process, the interface surface between the porous low-kdielectric layer and the diffusion barrier layer is rough, leading topoor adhesion between the porous low-k dielectric layer and thediffusion barrier layer, thereby reducing yield and electricalinterconnect performance of the semiconductor device.

For these and other reasons there is a need for the present invention.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention provide a method for manufacturinga semiconductor device. The method includes providing a semiconductorsubstrate, forming a porous low-k dielectric layer on the semiconductorsubstrate, forming a through-hole and a trench of a copper interconnectstructure, performing a helium plasma treatment on an exposed surface ofthe porous low-k dielectric layer, performing a nitrogen plasmatreatment on the exposed surface of the porous low-k dielectric layer toform a thin silicon nitride layer, and forming a diffusion barrier layeron bottoms and sidewalls of the through-hole and the trench of thecopper interconnect structure.

In one embodiment, the method further includes performing an argonplasma treatment on the silicon nitride layer. The argon plasmatreatment is performed at a flow rate in a range between 100 and 10,000sccm, a power in a range between 50 and 5000 W, and a pressure in arange between 0.1 mTorr and 10 Torr.

In one embodiment, the helium plasma treatment includes a helium flowrate in a range between 100 and 10,000 sccm, a power in a range between50 and 5000 W, and a pressure in a range between 0.1 mTorr and 10 Torr.

In one embodiment, the nitrogen plasma treatment is an in-situtreatment. The nitrogen plasma in-situ treatment includes a flow rate ina range between 100 and 10,000 sccm, a power in a range between 50 and5000 W, and a pressure in a range between 0.1 mTorr and 10 Torr.

In one embodiment, the nitrogen plasma treatment includes a gas mixtureof hydrogen, nitrogen, and argon.

In one embodiment, the silicon nitride layer has a thickness in a rangebetween 10 Angstroms and 80 Angstroms.

In one embodiment, the method further includes, after forming thediffusion barrier layer, filling the through-hole and the trench of thecopper interconnect structure with a copper interconnect layer, andperforming a chemical mechanical polishing process on the semiconductorsubstrate until a top surface of the porous low-k dielectric layer isexposed.

Embodiments of the present invention also provide a semiconductor devicecomprising: a semiconductor substrate, a porous low-k dielectric layer,a copper interconnect structure in the porous low-k dielectric layer, adiffusion barrier layer disposed between the copper interconnectstructure and the porous low-k dielectric layer, and a silicon nitridelayer disposed between the diffusion barrier layer and the porous low-kdielectric layer. In one embodiment, the silicon nitride layer has athickness in a range between 10 Angstroms and 80 Angstroms.

Embodiments of the present invention also provide an electronic devicecontaining the above-described semiconductor device.

The following description, together with the accompanying drawings, willprovide a better understanding of the nature and advantages of theclaimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view illustrating a trench and athrough-hole of a metal interconnect structure of a front-end deviceaccording to the prior art;

FIG. 1B is a cross-sectional view illustrating a diffusion barrier layerformed on the trench and the through-hole of the metal interconnectstructure of FIG. 1A according to the prior art;

FIGS. 2A through 2F are cross-sectional views depicting stages of amethod of manufacturing a semiconductor device according to anembodiment of the present invention;

FIG. 3 is a simplified flow chart of a method for manufacturing asemiconductor device according to an embodiment of the presentinvention; and

FIG. 4 is a cross-sectional view illustrating a semiconductor devicestructure according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, numerous specific details are provided fora thorough understanding of the present invention. However, it should beappreciated by those of skill in the art that the present invention maybe realized without one or more of these details. In other examples,features and techniques known in the art will not be described forpurposes of brevity.

It should be understood that the drawings are not drawn to scale, andsimilar reference numbers are used for representing similar elements.Embodiments of the invention are described herein with reference tocross-section illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of the invention.The thickness of layers and regions in the drawings may be exaggeratedrelative to each other for clarity. Additionally, variations from theshapes of the illustrations as a result, for example, of manufacturingtechniques and/or tolerances, are to be expected. Thus, embodiments ofthe invention should not be construed as limited to the particularshapes of regions illustrated herein but are to include deviations inshapes that result, for example, from manufacturing.

It will be understood that, when an element or layer is referred to as“on,” “disposed on,” “adjacent to,” “connected to,” or “coupled to”another element or layer, it can be disposed directly on the otherelement or layer, adjacent to, connected or coupled to the other elementor layer, or intervening elements or layers may also be present. Incontrast, when an element is referred to as being “directly on,”directly disposed on,” “directly connected to,” or “directly coupled to”another element or layer, there are no intervening elements or layerspresent between them. It will be understood that, although the terms“first,” “second,” “third,” etc. may be used herein to describe variouselements, components, regions, layers and/or sections, these elements,components, regions, layers and/or sections should not be limited bythese terms. These terms are only used to distinguish one element,component, region, layer or section from another region, layer orsection. Thus, a first element, component, region, layer or sectiondiscussed below could be termed a second element, component, region,layer or section without departing from the teachings of the presentinvention.

Relative terms such as “under,” “below,” “underneath,” “over,” “on,”“above,” “bottom,” and “top” are used herein to described a relationshipof one element, layer or region to another element, layer or region asillustrated in the figures. It will be understood that these terms areintended to encompass different orientations of the structure inaddition to the orientation depicted in the figures. For example, if thedevice shown in the figures is flipped, the description of an elementbeing “below” or “underneath” another element would then be oriented as“above” the other element. Therefore, the term “below,” “under,” or“underneath” can encompass both orientations of the device. Becausedevices or components of embodiments of the present invention can bepositioned in a number of different orientations (e.g., rotated 90degrees or at other orientations), the relative terms should beinterpreted accordingly.

The terms “a”, “an” and “the” may include singular and pluralreferences. It will be further understood that the terms “comprising”,“including”, having” and variants thereof, when used in thisspecification, specify the presence of stated features, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, steps, operations,elements, components, and/or groups thereof. Furthermore, as usedherein, the words “and/or” may refer to and encompass any possiblecombinations of one or more of the associated listed items.

The use of the terms first, second, etc. do not denote any order, butrather the terms first, second, etc. are used to distinguish one elementfrom another. Furthermore, the use of the terms a, an, etc. does notdenote a limitation of quantity, but rather denote the presence of atleast one of the referenced items.

The term “vertical” as used in this application is defined as a planeperpendicular to the conventional plane or surface of a wafer orsubstrate, regardless of the orientation of the wafer or substrate. Theterm “horizontal” refers to a direction perpendicular to the vertical asdefined above.

Embodiments of the invention are described herein with reference tocross-section illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of the invention.The thickness of layers and regions in the drawings may be exaggeratedfor clarity. Additionally, variations from the shapes of theillustrations as a result, for example, of manufacturing techniquesand/or tolerances, are to be expected. Thus, embodiments of theinvention should not be construed as limited to the particular shapes ofregions illustrated herein but are to include deviations in shapes thatresult, for example, from manufacturing. For example, an implantedregion illustrated as a rectangle will, typically, have rounded orcurved features and/or a gradient of implant concentration at its edgesrather than a discrete change from implanted to non-implanted region.Likewise, a buried region formed by implantation may result in someimplantation in the region between the buried region and the surfacethrough which the implantation takes place. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the actual shape of a region of a device andare not intended to limit the scope of the invention.

The present invention will now be described more fully herein after withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited by theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art.

Embodiment 1

FIGS. 2A through 2F are simplified cross-sectional views illustratingstages of process steps of forming a semiconductor device according toan embodiment of the present invention.

Referring to FIG. 2A, a semiconductor substrate 200 is provided.Semiconductor substrate 200 can be made of undoped silicon, dopedsilicon, silicon on insulator (SOI) and the like. By way of an example,semiconductor substrate 200 includes a monocrystalline silicon material.One or more isolation structures and well structures may be formed insemiconductor substrate 200, which are not shown herein for the sake ofclarity.

One or more front-end devices may be formed on semiconductor substrate200, which are not shown herein for the sake of clarity. The term“front-end” device is referred to herein as a semiconductor devicestructure before the back-end-of-the line (BEOL). The term front-enddevice is not intended to limit the semiconductor device structure to aparticular form disclosed.

Still referring to FIG. 2A, an etch stop layer 201 is formed onsemiconductor substrate 200, and a porous low-k dielectric layer 202 isformed on etch strop layer 201.

Etch stop layer 201 may be made of SiCN, SiC, or SiN, and functions asan etch stop layer at the time of forming a through-hole of a copperinterconnect structure to connect to a front-end device, and to preventcopper of the copper interconnect structure from diffusing into thefront-end device.

Porous low-k dielectric layer 202 may be made of low-k materials havinga dielectric constant k less than 4.0. Porous low-k dielectric layer 202may be made of, but not limited to, SiO2, SiCOH, hydrogen silsesquioxane(HSQ with k=2.5 to 2.9), methyl silsesquioxane (MSQ with k=2.2), SiCH,SiCNH, SiN_(x), and the like.

Porous low-k dielectric layer 202 may be formed using a spin-on-glass(SOG) coating process, rejection glue process, or chemical vapordeposition process. In an exemplary embodiment, porous low-k dielectriclayer 202 is formed using a plasma chemical vapor deposition process,for example, an organic silicon source gas can be used that comprisestwo source types of a chain structure and a ring structure, and an addedgas of a porogen (a pore-forming material) and an oxidizing agent(oxidizer). The organic silicon source gas can be selected from one orany combinations of tetramethylsilane (TMS), trimethylsilane (3MS), bistrimethylsilyl methane (BTMSM), methyldiethoxylane (DEMS), tetramethylcyclotetrasiloxane (TMCTS), tetravinyl tetramethyl cyclotetrasiloxane(TVTMCTS), trivinyl trimethyl cyclotrisiloxane (V₃D₃), decamethylcyclopentasiloxane (D₅). Porogens may include any suitable pore-formingmaterials. Porogens may include norbornene,5-dimethyl-1.4-cyclooctanediene, decalin, ethylbenzene, limozene, or anycombinations thereof. For example, porogens may include α-terpinene(ATRP), oxidizer may include O₂, N₂O, CO₂, or any combinations thereof.

Thereafter, the porous low-k dielectric layer is submitted to a curingtreatment to further reduce the dielectric constant while improving itsmechanical strength. The curing treatment may be performed in a furnaceor using other curing processes, such as ultraviolet curing, rapidthermal curing, flash curing, laser curing, and the like.

Referring to FIG. 2B, a copper interconnect structure 203 is formedincluding a though-hole 203 a and a trench 203 b. Through-hole 203 a andtrench 203 b of copper interconnect structure 203 may be formed usingany existing processes known to those of skill in the art, such as adual damascene process.

Thereafter, the exposed surface of the porous low-k dielectric layer issubmitted to a helium plasma treatment. The exposed surface of theporous low-k dielectric layer includes the bottom surfaces 203′ andsidewall surfaces 203″ of through-hole 203 a and trench 103 b of copperinterconnect structure 203. The exposed surface of the porous low-kdielectric layer also includes a top surface 203′. In an exemplaryembodiment, the helium plasma treatment includes a helium flow rate of100 to 10000 sccm, a power of 50 to 5000 W, a pressure of 0.1 mTorr to10 Torr. Through the helium treatment, the surface of porous low-kdielectric layer 202 becomes more dense.

Referring to FIG. 2C, porous low-k dielectric layer 202 is submitted toa nitrogen or a nitrogen-containing plasma treatment to form a thinsilicon nitride layer 204 on the exposed surface of the porous low-kdielectric layer.

In an embodiment, the nitrogen or nitrogen-containing plasma treatmentis performed in situ (nitrogen plasma in-situ treatment). The nitrogenplasma treatment on the exposed surface of porous low-k dielectric layer202 may be performed using hydrogen, nitrogen or argon gas or a gasmixture of hydrogen, nitrogen and argon. In one embodiment, thenitrogen-containing plasma treatment may be an ammonia (NH₃) plasmatreatment. In another embodiment, the nitrogen-containing plasmatreatment may be a hydrazine (N₂H₄) plasma treatment.

In an embodiment, the nitrogen or nitrogen-containing plasma in-situtreatment includes a nitrogen flow rate of 100 to 10000 sccm, a power of50 to 5000 W, a pressure of 0.1 mTorr to 10 Torr.

In an embodiment, through the reaction gas and suitable processparameters, a thin layer of silicon nitrite is formed on the exposedsurface of porous low-k dielectric layer 202. In an embodiment, the thinlayer of silicon nitride has a thickness in the range between 10Angstroms and 80 Angstroms. The thickness of the silicon nitride layermay be controlled by adjusting the nitrogen or nitrogen-containingplasma treatment process parameters. The thickness of the thin siliconnitride layer may be adjusted to ensure that the dielectric constant ofporous low-k dielectric layer 202 is within an appropriate range.

Thereafter, an argon or krypton plasma treatment is performed on theexposed surface of the porous low-k dielectric layer. The argon orkrypton plasma treatment is performed at a flow rate of 100 to 10000sccm, a power of 50 to 5000 W, a pressure of 0.1 mTorr to 10 Torr.Through the argon or krypton plasma treatment on the exposed surface ofthin silicon nitrite film 204, the surface of porous low-k dielectriclayer becomes more dense and smooth.

After the above-described steps, the porous low-k dielectric layer has adense and smooth surface that can improve the adhesion strength betweenthe diffusion barrier layer and the porous low-k dielectric layer.

Referring to FIG. 2D, a diffusion barrier layer 205 is formed onsidewalls and bottoms of copper interconnect infrastructure 203. In theembodiment, diffusion barrier layer 205 is formed by a physical vapordeposition process that is performed at a temperature of about −40° C.to 400° C. and under a pressure of about 0.1 mTorr to about 100 Torr.Diffusion barrier layer 205 may be made of a metal or a metal compound,such as tantalum, tantalum nitride, titanium, titanium nitride,zirconium nitride, titanium-zirconium nitride, tungsten, tungstennitride, alloys and combinations thereof.

Referring to FIG. 2E, a copper interconnect layer 206 is fillingthrough-hole 203 a and trench 203 b of copper interconnect structure203. In the embodiment, copper interconnect layer 206 is filled using aplating process. In order to enhance adhesion between copperinterconnect layer 206 and diffusion barrier layer 205, a copper seedlayer is first formed on diffusion barrier layer 205 prior to formingcopper interconnect layer 206. The copper seed layer is not shown inFIG. 2E for clarity.

Thereafter, a chemical mechanical polishing process is performed toexpose the top surface of porous low-k dielectric layer 202.

The above-described process steps complete the copper interconnectstructure.

According to the present invention, the surface of the copperinterconnect structure is dense and smooth through subsequent heliumplasma, nitrogen plasma and argon plasma treatments, thereby increasingadhesion of the diffusion barrier layer formed thereon and improvingreliability and yield of the semiconductor device.

FIG. 3 is a simplified flow chart of a method 300 for fabricating asemiconductor device according to an embodiment of the presentinvention. Method 300 includes:

Step 301: providing a semiconductor substrate; forming a porous low-kdielectric layer on the semiconductor substrate; forming a through-holeand a trench of a copper interconnect structure in the porous low-kdielectric layer;

Step 302: performing a helium plasma treatment on the exposed surface ofthe porous low-k dielectric layer;

Step 303: performing a nitrogen or nitrogen-containing plasma treatmenton the exposed surface of the porous low-k dielectric layer to form athin silicon nitride layer;

Step 304: performing an argon or krypton plasma treatment on the thinsilicon nitride layer;

Step 305: forming a diffusion barrier layer on the bottom and sidewallsof the through-hole and the trench of the copper interconnect structure;

Step 306: filling the through-hole and the trench of the copperinterconnect structure with a copper interconnect layer;

Step 307: performing a chemical mechanical polishing process to expose atop surface of the porous low-k dielectric layer.

Embodiment 2

FIG. 4 is a cross-sectional view illustrating a semiconductor devicestructure 40 according to an embodiment of the present invention.Semiconductor device structure 40 includes: a semiconductor substrate400; a porous low-k dielectric layer 402 disposed on semiconductorsubstrate 400. In an embodiment, an etch stop layer 401 may be disposedbetween semiconductor substrate 400 and porous low-k dielectric layer402. Semiconductor substrate 400 may be of an undoped silicon, dopedsilicon, silicon on insulator, and the like. By way of example,semiconductor substrate 400 is made of a monocrystaline silicon.Semiconductor substrate 400 may include isolation structures and variouswell structures, which are not shown for the sake of clarity.Semiconductor substrate 400 may include one or more front-end devices(not shown) formed thereon. A front-end device is referred to asemiconductor structure that has not gone through the back-end-of-theline (BEOL) process.

Etch stop layer 401 may include SiCN, SiC, SiN, or any combinationsthereof.

Porous low-k dielectric layer 402 may be made of low-k materials havinga dielectric constant k of less than about 4.0. Porous low-k dielectriclayer 402 may be made of, but not limited to, SiO2, SiCOH, hydrogensilsesquioxane (HSQ with k=2.5 to 2.9), methyl silsesquioxane (MSQ withk=2.2), SiCH, SiCNH, SiN_(x), and the like.

Semiconductor device structure 40 may further include a copperinterconnect structure 403 disposed in porous low-k dielectric layer402. Copper interconnect structure 403 is connected to a front-enddevice disposed on semiconductor substrate 400.

Semiconductor device structure 40 also includes a diffusion barrierlayer 405 disposed between porous low-k dielectric layer 402 and copperinterconnect structure 403, and a thin silicon nitride layer 404disposed between porous low-k dielectric layer 402 and diffusion barrierlayer 405. Because silicon nitride layer 404 has a smooth and densesurface, the adhesion strength between diffusion barrier layer 405 andsilicon nitride layer 404 has increased. Diffusion barrier layer 405 ismade of a metal or a metal compound, such as tantalum, tantalum nitride,titanium, titanium nitride, zirconium nitride, titanium-zirconiumnitride, tungsten, tungsten nitride, alloys and combinations thereof. Inan embodiment, thin silicon nitride layer 404 has a thickness in therange between about 10 Angstroms and about 80 Angstroms.

According to the present invention, a semiconductor device manufacturedusing the above-described process steps includes an interface layerbetween the porous low-k dielectric layer and the diffusion barrierlayer. The smooth and dense surface of the interface layer increases theadhesion strength of the porous low-k dielectric layer and the diffusionbarrier layer, and improves reliability and yield of the semiconductordevice.

Embodiment 3

Embodiments of the present invention provide an electronic deviceincluding a semiconductor device that is manufactured by theabove-described method of embodiment 1 or the above-described devicestructure of embodiment 2.

In accordance with the present invention, the electronic device may be amobile phone, a laptop computer, a netbook, a tablet PC, a game console,a TV, a DVD player, a GPS device, a camera, a voice recorder, MP3, MP4,PSP players, and other semiconductor devices including intermediateproducts and electronic components that are manufactured using theabove-described method to improve reliability and yield.

While the present invention is described herein with reference toillustrative embodiments, this description is not intended to beconstrued in a limiting sense. Rather, the purpose of the illustrativeembodiments is to make the spirit of the present invention be betterunderstood by those skilled in the art. In order not to obscure thescope of the invention, many details of well-known processes andmanufacturing techniques are omitted. Various modifications of theillustrative embodiments as well as other embodiments will be apparentto those of skill in the art upon reference to the description. It istherefore intended that the appended claims encompass any suchmodifications.

Furthermore, some of the features of the preferred embodiments of thepresent invention could be used to advantage without the correspondinguse of other features. As such, the foregoing description should beconsidered as merely illustrative of the principles of the invention,and not in limitation thereof.

What is claimed is:
 1. A semiconductor device comprising: asemiconductor substrate; a porous low-k dielectric layer; a copperinterconnect structure in the porous low-k dielectric layer and having athrough-hole in direct contact with an upper surface portion of thesemiconductor substrate; a diffusion barrier layer disposed between thecopper interconnect structure and the porous low-k dielectric layer andcovering a bottom of the through hole; and a silicon nitride layer indirect contact with sidewalls of the porous low-k dielectric layer in adirection perpendicular to a planar surface of the semiconductorsubstrate.
 2. The semiconductor device of claim 1, wherein the siliconnitride layer has a thickness in a range between 10 Angstroms and 80Angstroms.
 3. An electronic device comprising the semiconductor deviceof claim
 1. 4. The semiconductor device of claim 1, further comprisingan etch stop layer disposed between the semiconductor substrate and theporous low-k dielectric layer and having an opening for passing throughthe through-hole and having sidewalls covered by the diffusion barrierlayer.
 5. The semiconductor device of claim 4, wherein the etch stoplayer comprises one of SiCN, SiC, and SiN.
 6. The semiconductor deviceof claim 4, wherein the silicon nitride layer comprises a portion incontact with an upper surface of the etch stop layer.
 7. Thesemiconductor device of claim 1, wherein the porous low-k dielectriclayer comprises one of SiO2, SiOH, hydrogen silsesquioxane, methylsilsesquioxane, SiCH, SiCNH, and SiN.
 8. The semiconductor device ofclaim 1, wherein the silicon nitride layer is not in contact with thesemiconductor substrate.
 9. The semiconductor device of claim 1, whereinthe silicon nitride layer is in direct contact with an upper surface ofthe porous low-k dielectric layer in a lateral direction to thesemiconductor substrate.
 10. The semiconductor device of claim 1,wherein the diffusion barrier layer comprises a metal or a metalcompound.
 11. The semiconductor device of claim 10, wherein the metalcompound comprises at least one element selected from the groupconsisting of tantalum, titanium, zirconium, and tungsten.
 12. Thesemiconductor device of claim 1, wherein the silicon nitride layer isdisposed between the diffusion barrier layer and the porous low-kdielectric layer.